PUMP GP-PISTON 3487627 - Caterpillar

Illustration 1. Setup for using external source of air pressure.
Work carefully around an engine that is running. Engine parts that are hot, or parts that are moving, can cause personal injury.
5. Start the engine and apply an air pressure of 70 kPa (10 psi) to arm (activate) the fuel ratio control. Now lower the air pressure to the specified arming pressure.6. Remove the plug from the right front corner of the top cover. See Illustration 2. Put a 3/16" hex wrench through the hole in the top cover until it engages the fuel limit adjustment screw. Turn the adjustment screw clockwise until engine speed starts to drop. The engine should stop. Count and record the number of turns required for adjustment so you can use this same setting later in this procedure.
Illustration 2. Location of screw for fuel limit adjustment.7. Shut off engine if it did not stop in previous step. Remove the aluminum plug from top of fuel ratio control. Use a pair of locking pliers to grip and turn out this plug.8. Use a 1/8" hex wrench to turn the arming adjustment screw two turns clockwise. See Illustration 3.
Illustration 3. Location of arming adjustment screw.9. Start engine and apply the specified arming pressure to the fuel ratio control. See Step 1.10. Turning arming adjustment screw counterclockwise slowly until engine speed begins to drop. This is the correct setting for the arming adjustment screw. Check this setting as follows: (a) Stop engine and wait one minute for oil pressure to drop.(b) Reduce the air pressure to the fuel ratio control to zero and start the engine.(c) Raise the fuel ratio control air pressure until the control causes the engine speed to drop. Note this pressure.(d) If the arming pressure found in Step (c) is not correct, turn the arming adjustment screw clockwise to increase arming pressure. Go back to Step (a) to recheck arming pressure.11. Shut off the engine and reduce air pressure to zero that is connected to the fuel ratio control.12. Turn fuel limit adjustment screw counterclockwise the same number of turns as recorded in Step 6 to put the adjustment back to its original setting.13. Start engine and again apply the specified arming pressure to the fuel ratio control. Then reduce the air pressure to zero.14. Rapidly move the speed control shaft in the speed increase direction. The dial indicator will go up to the fuel limit position, pause momentarily, then drop back. Do this several times and read the dial indicator during each pause. Or, load the engine until the dial indicator stops. where the dial indicator pauses or stops, is the limit for fuel control linkage movement set by the fuel ratio control. If the dial indicator does not pause or stop, arming adjustment is not correct. See Step 10. Apply air pressure above arming pressure specified to the fuel ratio control. Reduce air pressure to zero and repeat Step 14.15. Adjust the fuel limit by turning the adjustment screw. turn adjustment